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Watch rain and shadows from Saturn’s rings give the planet a funky ionosphere

If you’ve ever picked up a radio broadcast from thousands of kilometers away, you’ve interacted with Earth’s ionosphere, the layer of our atmosphere that reflects radio signals and helps protect us from solar radiation. Saturn has a dense ionosphere, too, one that has similarities and differences to our own, some of the final data from NASA’s Cassini mission reveal. Before it plunged into the planet as part of its “Grand Finale” in September, the spacecraft took measurements as it passed inside Saturn’s enormous rings. These rings affect the way the ionosphere is charged, researchers report today in Science. When the probe passed into the shadow Saturn’s two largest and brightest rings—the A and B rings—cast on the planet, the amount of ionized plasma dropped immensely, meaning the ionosphere is far less active while in the ring shadow. However, there is still a small amount of plasma movement in this shadow zone. This extra activity may be coming from Saturn’s innermost ring: the D-ring. Researchers theorize that ring rain, an interaction where charged water particles migrate from the rings to the ionosphere, may explain this phenomenon. Good news for any future saturnian ham radio operators.